The invention relates to an apparatus for the connection of articles via at least one connection element plasticizable by heat, the apparatus having a heatable cap, which is movable toward and away from the connection element and which has a shaft, for the forming of a rivet head at the connection element and having means for the direct heating of the cap.
Apparatus of this kind work according to the so-called rivet peg welding principle according to which a projection, the so-called rivet peg, formed at a connection element attached to one of the articles is pushed through an opening of the other article and is then provided with a shaped rivet head at the free end of the rivet peg. The connection element in this respect can also be made from a separate component which is pushed through both articles and has an already attached head at one end.
The shaping of the rivet head takes place, when the described welding principle is used, in that the rivet peg is plasticized by heating and is brought into the shape desired in the individual case by means of a tool called a cap in the following and pressed against the rivet peg. In this respect, at least one of the two joining partners is usually made from a plasticizable plastic, although it is also sufficient in principle, however, if only the involved connection elements or the rivet pegs provided thereon are made from a plasticizable material.
An apparatus of the initially named kind is described in DE 10 2004 057 453 B3. In this respect, a rivet cap is coupled to a heat source and is heated. As soon as the cap has reached a temperature which is above the softening point of the material to be processed, it is lowered onto the tool and reshapes a rivet peg into a rivet head. Subsequently, the rivet cap is decoupled from the heat source and thereby cooled. The heat source includes an electric heating coil which is operated continuously. To cool the cap, the heat source including the electric heating coil is separated from the cap before the removal of the cap from the rivet head. The construction effort required for this is relatively large.
It is the underlying object of the invention to provide an improved apparatus of the initially named kind with which the previously mentioned disadvantages have been eliminated. In this respect, in particular a fast heating of the cap should also still be maintained with a minimized construction effort.
The object is satisfied in accordance with the invention in that the means for the direct heating of the cap include at least one ceramic heating element.
The invention thus inter alia exploits the circumstance that ceramic heating elements take up relatively little space and have a relatively fast heating rate. Furthermore, ceramic heating elements have a relatively low mass so that they can be cooled relatively quickly again.
In this respect, the ceramic heating element is preferably in direct contact with the cap body. It can, in particular, be fixedly connected to the cap.
In accordance with a preferred practical embodiment of the apparatus in accordance with the invention, the ceramic heating element is pressed toward the cap body.
It is in particular also of advantage if the ceramic heating element has an annular shape and is attached to the cap shaft in direct contact with the cap body.